Permanent anti-fog properties are desired in several applications such as ophthalmic and sun lenses; safety, military and sports eyewear and accessories; glazing for automotive, transportation, building and construction, greenhouses; industrial, point-of-sale and electronics displays; commercial refrigerators and freezer doors; mirrors; solar panels, and others.
Fogging occurs when the water vapor from surrounding air condenses on an article forming small water droplets. This happens when the article is at a lower temperature than that of the environment. Current anti-fog coatings usually form smooth surfaces that are hydrophilic in nature. Surfactants are used in the coating formulation to increase the surface energy of the cured coatings enabling the droplet to sheet instead of forming spherical droplets on the substrate. The resulting water sheeting effect minimizes the scattering of light thereby improving visibility.
In order to have long-lasting, or permanent, anti-fog performance, anti-fog coatings are typically formulated with large amounts of surfactants that can considerably lower the hardness of the coatings. However, oftentimes, the anti-fog coatings lose the anti-fog functionalities rather quickly, and need to be rejuvenated with additional surfactants. Moreover, the long-lasting anti-fog coatings available on the market today are principally thermally cured and thus require long cure times at elevated temperatures that can impact manufacturing cost and productivity of anti-fog article manufacturers. Additionally, many of these coatings do not have abrasion resistant properties. Accordingly, there is a need for new fast-curing anti-fog coatings with long-lasting anti-fog properties without the need for rejuvenation, and, optional, better abrasion resistant properties.